Virgin Atlantic's rocket planes may soon be taking to the skies once more, as the would-be space tourism company is awarded an operator license for its SpaceShipTwo craft.

The license, granted by the US Federal Aviation Administration's Office of Commercial Space Transportation, will pave the way for commercial flights, Virgin Galactic said in a statement. The company has also started taxi tests of new SpaceShipTwo craft VSS Unity, ahead of flight tests.

The granting of this license is a step towards getting Virgin Atlantic's spaceships back into the airborne testing phase, following a crash in October 2014 that killed pilot Michael Alsbury and seriously injured co-pilot Peter Siebold.

In the wake of that disaster -- which was ruled by the US National Transportation Safety Board to be due to co-pilot error and inadequate safety procedures -- Virgin founder Richard Branson vowed to continue pursuing commercial space flight. "Space flight is hard," he said, "but worth it."